Automobile airbag systems have been developed to protect vehicle occupants in the event of a crash by rapidly inflating a cushion or bag between a vehicle occupant and the interior of the vehicle. The inflated airbag absorbs the vehicle occupant's energy to provide a gradual, controlled deceleration and provides a cushion to distribute body loads and keep the occupant from impacting the hard surfaces of the vehicle interior.
The use of such protective gas-inflated airbags to cushion vehicle occupants in crash situations is now widely known and well documented. The requirements of a gas generant used in an automobile airbag inflator are very demanding. The gas generant must have a burning rate such that the airbag is inflated rapidly (within approximately 30-100 milliseconds) and the burning rate must not vary over long term storage (aging and/or thermal cycling) or as a result of shock and vibration encountered during the life of the vehicle. The burning rate must also be relatively insensitive to changes in humidity and temperature. When pressed into pellets, wafers, cylinders, discs or whatever shape, the hardness and mechanical strength of the gas generant bodies must be adequate to withstand the conditions to which they will be exposed without any fragmentation or change of exposed surface area. Excessive breakage of the generant bodies will lead to system failure where, for example, an undesirable high pressure condition will be created within the inflator, possibly resulting in catastrophic rupture of the inflator housing.
Much effort has also been expended on the development of inflator housings. The housings are the metal shells in which the gas generants are placed and ignited when an airbag needs to be inflated. This housing is fitted with the airbag and together, they form a critical part of any automobile airbag system. Engineers of automobile airbag systems understand that the design of the inflator housing can influence the performance of the gas generant and the overall protection of the vehicle occupant.
The gas generant must efficiently produce a relatively cool, non-toxic, non-corrosive gas which is easily filtered to remove solid and liquid combustion by-products. This filtering is needed to preclude damage to the inflatable airbag or injury to the occupant of the automobile. These requirements limit the applicability of many otherwise suitable chemical compositions, shapes and configurations from being used in automotive airbag inflators. Gas generants can also be used for fire extinguishing. Recently, a number of companies have begun using the gases produced by solid energetic or pyrotechnique materials for fire extinguishing.
The invention, as it relates to the inflator housing, comprises the use of a metal ribbon with a plurality of apertures and a segment of expanded metal that is rolled into a coil and used as a filter to trap combustion products. The following discussion of the background art will assist the artisan in understanding the advancements that the present invention brings to the industry.